Early therapeutic response assessment by 18FDG-positron emissiontomography during chemotherapy in patients with diffuse large B-celllymphoma: isolated residual positivity involving bone is not usually a predictor of subsequent treatment failure

Abstract

Residual 2-fluoro-2-deoxyglucose (FDG) – positron emission tomography (PET) positivity during treatment of patients withdiffuse large B-cell lymphoma (DLBLC) prospectively identifies a subgroup at high likelihood of subsequent treatmentfailure. A single institution clinical audit of FDG-PET performance for this indication was undertaken for patients withDLBCL treated with anthracycline-based chemotherapy+radiotherapy. Of 45 eligible patients, 14 (31%) were PETpositiveafter a median of three chemotherapy cycles (range 1 – 5), of which 10 (71%) progressed at a median of 6.5 months.An interim positive PET was a statistically significant adverse prognostic factor for treatment failure (P=0.0001, log-rankanalysis) with a hazard ratio for a positive interim-treatment PET of 9 (95% confidence interval 4 – 55) and positivepredictive value of 71% and negative predictive value of 90%. Notably, four patients with low-grade FDG-avidity limited tosites previously involved by biopsy-proven osseous lymphoma, remain progression-free (median follow-up 62 months). LowgradeFDG-avidity on interim restaging at sites of bone involvement by DLBCL at diagnosis, appears to be less predictive ofdisease progression than residual nodal or extra-nodal soft tissue abnormality by PET.